Piracy is an increasing problem faced by video and image content owners, such as companies that produce, market, and distribute motion pictures, as well as artists, photographers, or the like. In some instances, the piracy takes the form of unauthorized downloading, duplication, or leaking of video or image content, whether voluntary or not. In other instances, piracy takes the form of unauthorized adaptation, editing, or other transformation of the video or image content.
To combat piracy, digital watermarking schemes have been introduced. Digital watermarking involves altering a digital representation of the video or image content. Typically, this alteration is not perceptible to the human eye. The digital watermark can serve as a digital “fingerprint” that associates a given person with a given copy of the content. Should this copy of the content be compromised afterwards, the “fingerprint” may facilitate forensic analysis of the compromised content. Also, the digital watermark can support authentication functions, such as ensuring that a given media player can play the content only if the content is properly licensed. For example, when a person obtains a license to play given content, the licensee may be provided a copy of the content with a watermark embedded therein. Afterwards, when the licensee wishes to play the content on a media player equipped with a watermark detector, the media player can test the content to see if the watermark is embedded therein. If the watermark is present and intact, the content is probably authentic and is played. Otherwise, the media player can reject the content.
In response to these watermarking schemes, content pirates have devised attacks against watermarked video or image content that are designed to undermine, defeat, or destroy the watermarks. These attacks may also be designed to fool the watermark detector. For example, a dishonest licensee may wish to defeat the watermark on his or her licensed copy of the content, so as to defeat the forensic function of the watermark. Then, the dishonest licensee could distribute the “unwatermarked” copy of the content without the copy being traceable back to him or her. The same motivation may apply to a person who is not a licensee.